Citizens are asked not to go to crowded areas and cities located close to the Turkish-Syrian border

US Consulate General in Istanbul, warned its citizens of the dangers that may be for Americans and other foreigners extremist groups in Istanbul, reports ABC News.

Attacks extremists can be pre-planned or occur without warning. They can include armed attacks, kidnapping attempts, bombings and other acts of violence, said in a statement.

Consulate General called on citizens to exercise increased vigilance and caution crowded areas, including the popular tourist destinations, as well as political rallies. Citizens are also urged not to visit towns in southeast Turkey, especially those located near the Turkish-Syrian border.